Good question!
Ran it all last season and don’t recall having issues with battery life to any significant extent. And by that I mean: As long as I wasn’t trying to run full screen brightness all day and then try to run well into the evening too. In that scenario, the daytime run and gun did present a few issues just because I was using it as a GPS to move around and as a sonar. Those days I was able to solve the problem as the sun was going down by just having a second battery on hand and swapping out. That said, not sure the additional cost would be worth it to go lithium even though maybe the weight savings would be nice.
Coincidentally, the only other issue I had, I had to send the unit to HB for warranty repair.